Fluorescent light circuit



Feb. 2, 1960 E. w. BANIOS FLUORESCENT LIGHT CIRCUIT 2 Sheets-Sheet 2Filed Sept. 20, 1957 Z L 1% "H i 4% a. a v 7 2 L/ 1 7 k 7 J W mvw wk 0A? 2 m & v 5/ i 2 z I a W w 1 5 3 1 W WW 7 Maw ,mw

United States Patent FLUORESCENT LIGHT CIRCUIT Edward W. Banios,Hawthorne, Calif., assignor to Douglas Aircraft Company, Inc., SantaMonica, Calif.

Application September 20, 1957, Serial No. 685,171

4 Claims. (Cl. 315-100) This invention relates to fluorescent lighting,particularly lighting systems or circuitry for use under the severeconditions encountered in the cabins of high altitude transportaircraft.

Conventional fluorescent lighting systems, even those designedespecially for aircraft use, exhibit certain characteristics which donot quite meet established requirements. Among other failings thereofmay be mentioned the fact that their efliciency in low ambienttemperatures is definitely low.. For example, at0 F. their actualefficiency is only 18% of rated efiiciency, yet transport aircraft oftenfly in air-strata the temperature of which is 50 F.

More significant, perhaps, is the fact that, in an aircraft cabin, theconventional fluorescent lamp not only is a non-instantaneous starter,butwill not. startwat all at any temperature below about 40 F.

The average servicelife of such lamps is of the order of 2500 hours, andabout 74 of them are required in each cabin, which facts necessitate alltoo frequent replacement of these lamps.

Controlled dimming of the ordinary fluorescent lamp is not practical,for if it is attempted to any useful extent, the lamp will extinguish.In any event, when the lamp is about to burn out, it does so in aprolonged series of intermittent flashes which annoy the passengers.

Again, as the wattage-capacity of the conventional fluorescent lamp lineincreases, a weight-penalty is incurred and with 74 high-wattage lampsused in one cabin, this penalty can no longer be ignored.

No standard preheat fluorescent light installed in conventionalcircuitry therefor can be made to start at a rate that can be properlydesignated instantaneous, for a noticeable period of time elapsesbetween closing of the circuit and incandescence of the lamp.

This invention provides a fluorescent lighting system and circuitrywhich, although its lamps consist, as usual, of a sealed transparenttube containing a rare, atmospheric gas under low pressure, with theinner surface of the wall of the tube coated with a phosphor totransform the ultra-violet radiations of its electric arc into visiblelight, nonetheless removes the aforestated and other deficiencies offluorescent ligths when used in transport, or high altitude, aircraft.

The present unit comprises one or more such lamps and associatedappurtenances configured in close circuit therewith. What ever specificform the electrical configuration may take, it essentially includes anelectrical ballast and a reactor in series, the lamp being connected inparallel with one of the aforementioned units in this series circuit.The paramatric values of the ballast and capacitor are made such thatthe reactances of the ballast and the reactor are rendered equal so thatthe seriescombination will resonate at the usual frequency of the AC.source, which is of the order of 400 c.p.s. When the lamps switch isclosed, this resonant circuit permits sufficient current to flow throughthe filaments of the 2,923,854 Patented Feb. 2, 1960 lamp to suddenlyraise theirtemperature, while a voltage large enough to are the lampthrough the pressurized gas therein is, by this same resonancephenomenon, generated across the capacitor. The result is substantiallyinstantaneous starting in all circumstances except with extremely lowvoltage and in ambient temperatures below -40 F. Theelectrical ballastmember, Whether it be an inductance or a capacitor, thereafter acts tolimit the current flowing to the lamp, whereas the reactor, either acapacitor or an inductance permits continuance of the filament heating.

A grounded plate, which may be the altered reflector or the frame of thelamp or metallic foil adhered to the tube, is disposed in closerproximity to the lamp than the conventional reflector or frame and isotherwise so constructed and configured as vto serve to lower thestarting voltage required, as well as to stabilize low voltage operationand low temperature starting and operation. It is believed that :theincorporation of this plate sets up a ground reference plane very closeto the rear atmospheric gases in the tube in such a manner as to therebycreate greater ionization in these gases. This augmented ionizationenables lower-voltage starting and starting at. lower ambienttemperatures than Wise possible.

The device may be employed for dimmingservice the-incorporationtherewith, in the usual manner, of the standard variableauto-transformer for varying the circuit terminal voltage.

The circuit terminal voltage is non'critical and the filaments arecontinuously heated, prolonging the lamp life, which". is of the orderof 10,000 hours with 3,000 starts. No starter is incorporated, obviatingstarter trouble and starter replacements. When the lamp fails, it doesso sharply, instead of flickering in the usual manner.

Despite these advances, the weight-penalty imposed is small, compared tothat incurred in increasing the wattage of conventional fluorescentlamps. For example, compared to the latter there are, in the presentlamp and system, 1, 3, 4 and 6 ounce penalties, respectively, inincreasing the wattage to 8, 15, 20 and 25 watts and no weight penaltyat all at the 6 watt capacity. There is a 3 ounce weight saving in thepresent 30 watt circuit. v

Other improved features and advances achieved by the invention willeither be made manifest, or become apparentyhereinafter.

In order to render these and other concepts more concrete, several ofthe presently preferred. embodiments thereof are shown in theaccompanying drawings and are described hereinafter in conjunctiontherewith.

In these drawings, Fig. 1 is a diagrammatic view of that form of thepresent invention in which the fluorescent lighting circuit utilizes alagging power factor;

Fig. 2 is a similar view in which the fluorescent lighting circuitemploys a leading power factor;

Fig. 3 is a similar view in which a trimming capacitor isincorporatedinto the circuitry of Fig. 1;

Fig. 4 shows this trimming capacitor employed in the circuitry of Fig.2;

Fig. 5 illustrates the circuitry of Fig. 1 as applied to a plurality oflamps in bank arrangement;

Fig. 6 depicts the circuitry of Fig. 2 applied to a plurality of lamps,the bank including means for stabilizing operation; and also includingan ionizing condenser that affords smoother dimming with higher dimmingratios by virtue of the higher ionizing potential established by theadditional condenser; and

Fig. 7 is a diagram of circuitry that includes'an ionizing condenser forsmoother dimming with higher dimming ratios.

The unit shown in Fig. 1 includes an A.C. source 12, one pole 12A ofwhich is grounded. The A.C. frequency is preferably 400 c.p.s. Connectedin series with the output or positive, pole of the source, by means of aconductor path 12B, is an inductive ballast 13 having a coil 14 and acore, not shown. Further in series with the source 12 is a capacitor 17.

The lamp, including the usual tube 18, is shunted across the conductorpath 12B between the ballast 13 and the capacitor 17, the positivefilament, or anode, 19, being series-connected in 12B at thisintermediate point and the negative filament, or hot cathode 20, beingconnected in 12B intermediate the capacitor 17 and the pole 12A of thesource.

An ionization-augmenting plate 22, which may be the reflector or frameof the lamp, is disposed in close proximity to the one side of the lampand is connected by a ground-wire 23 to the grounded leg of theconductor path 12B. It seems that the plate 22 serves as a groundreference plane for the rare atmospheric gases in the tube and otherwiseaugments the ionization therein. The augmented ionization minimizes thestarting voltage necessary and also enables instantaneous starts at verylow ambient temperatures. The effect of plate 22 becomes more marked asthe original ionizing potential across the lamp decreases and also asthe gas becomes less active at lowered ambient temperatures. The closerthe element 22 is placed to the lamp, the better the low-end operationof the lamp. The invention contemplates that 22 may take the form of astrip of metallic foil coating one side of the lamp which is grounded,as Well as taking one of the aforementioned forms.

Electric current flow through the lamp is preferably initiated bypassing a current through the filaments and thus permitting applicationof a materially smaller voltage between them to vaporize the mercury andeffect a gaseous electric discharge between electrodes. This isdesignated the cathode pre-heat type of lamp. It is conducive to longerelectrode life, for during the conventional cold start, some of theelectrode surface material is boiled off by the arc, whereas in thepresent instance no such damage occurs, since both electrodes soon reacha temperature of 950 C. At such elevated temperature, the electrodereadily emits copious quantities of thermionic radiation, or electrons,which substantially instantly effect a gaseous electric discharge in thelamp.

It is preferred that the lamp tube be coated, on its inner surface, withsome well-known phosphor or phosphorescent compound which produces awarm-white light.

The conventional 30 watt ballast is of the auto transformer type, butballast 13 is, in contrast, a series choke ballast, preferably rated as95-100/mh. and 600 ma., for the present resonant-start circuit.Preferably, for the present lamp when rated at 30 watts, the capacitor17 has a rating of 1.75 microfarads.

This circuit can be constrained to afford dimming by means of having thevoltage across it varied by the incorporation of a well-known variableauto-transformer in the conventional hook-up, if desired. By virtue ofthe resonance, the lamp dims instantaneously throughout its range. Itcan be instantly extinguished while ve dim and relit instantly at thissame level. I

The proportions of the lagging and leading power factor circuits canreadily be so chosen that the system power factor can be easilycorrected, or rendered equal to unity.

Because of the ability to employ an unconventionally high power sourcefrequency, it is feasible to operate the lamp at 810% higher currentsthan in conventional, giving about 810% more light output than usual.

The lagging power factor has been found to have almost linear dimmingcharacteristics when used with the present lamps, especailly those thathave seen service, that is, have aged.

In another one of the presently preferred embodiments of the invention,such as that illustrated in Fig. 2, a leading, instead of a lagging,power factor A.C. source, 12C, is employed. Also, the positions andfunctions in the circuit of the capacitor and the inductanceaforementioned are, here, reversed, the capacitor device 17 now beingdisposed between the lamps input terminal and the A.C. source andserving as a ballast device, while the inductance device 13 isconstrained to serve as an inductive reactor. Otherwise, theconfiguration is the same. The ballasting capacitor 17 limits thecurrent received by the lamp so that the resulting current leads theterminal voltage. Thus, for a 20 watt unit, for example, the circuit hasa leading power factor of the order of .500. The other characteristicsof this unit are the same as for the lagging power factor unit exceptthat in Fig. 2 the inductive power factor is not so low. However, thissecond species of unit, having a low leadingpower factor is capable ofcorrecting the systems power factor if it lags too much.

An equal amount of each of the circuit capacity and arrangeemnt of Figs.1 and 2 is contemplated as feasible for use, so as to produce unitypower factor; or the leading power factor species could be so combinedwith the lagging species as to correct an overly-lagging power factor ofthe system.

It is to be noted that the unit or circuitry of Fig. 2 possesses anon-linear dimming characteristic as contrasted to the substantiallylinear dimming propery of that of Fig. 1; however, in Fig. 2 the age, orextent of use of the lamp plays a smaller role, in low-level lampoperation, than it does in the aforesaid circuit with a lagging powerfactor.

Another embodiment of the invention is shown in Fig. 3. Here, the systemis substantially the same as that of Fig. '1 with the inclusion of acapacitor 24 for enabling the establishment of a highly tuned resonantcircuit during lamp pro-arcing conditions while preventing passage ofexcessive current through the electrodes 19 and 20. eeue onpu on; s;ueuoduioo eAnonpur Arno out stem 13, and the two capacitors coact toform the main capacitative components of the system. It is accordinglyunnecessary to enlarge the capacitor 17, for such would afford excessivecurrent fiow through the electrodes. instead, the needed extracapacitance for effecting an unusually highly tuned resonant circuit issupplied by capacitor 24, in Fig. 3, which capacitor cannot have anydetrimental effect upon the electrodes, such as arcing and burning out.However, the combination 13 to 24, inclusive, is here so designed thattheir components remain far enough away from mutual resonance as to failto pull a large current when the lamp is being removed or when afilament burns out.

Fig. 4 shows a system essentially like that of Fig. 3 so far as theadditional capacitor is concerned, but the circuitry is otherwise likethat of Fig. 2; that is, the inductance 13 and capacitor 17 are here inthe Fig. 2 positions.

In Fig. 5, the specific circuitry of Fig. 3 is shown as employed tooperate a plurality, or a bank, of the lamps 18 arranged in series, eachof the lamps being provided with a grounded reflector 22, a singletrimming capacitor 24 being employed for all three lamps. Instantaneousstarting of all these lamps, simultaneously, is assured by thiscircuitry, for the generic reasons set forth hereinabove.

In Fig. 6, the principle of Fig. 4 is shown as employed to effectuatesubstantially instantaneous starting of a plurality of lamps, 18,arranged in series as a bank. In addition, however, the negativefilament or electrode of the one lamp is connected to the positivefilament of the next lamp by a condenser, 46 in each of the legs of theconnecting conductor path. Condensers 4i constitute means setting up anoperation-stabilizing circuit for the lamps that becomes quite effectiveupon completion of the starting phase.

The circuitry of Fig. 7, by incorporating a capacitor 26.

between reflector 22 and the negative lamp-ele'ctrodeZl),

establishes an ionization augmenting potential difference between theelectrodes 19, 20 and reflector 22, so as to afford smoother dimmingaction, while exhibiting still higher dimming ratios. That is, capacitor26 raises the potential of electrode 20 with respect to plate 22 ineffecting the aforesaid augmentation of ionization.

Whatever variant of the basal circuits of Figs. 1 and 2 may be employed,therefore, the invention requires that the particular circuit (1) besuch as to establish a resonant condition therein prior to the actualarcing of the lamp, preferably by impressing the generated voltageacross one of the resonating reactors in circuit across the lampelectrodes and (2) to supply a ballasting series impedance for the lampduring the lamps post arcing period. The invention also provides meansto heat the lamp filaments by passage of current therethrough inconjunction with arc-impingement thereon, in order to smooth out theoperation of the circuit and the lamp during starting and dimming of thelamp.

Although certain shapes, compositions and parameters have been recitedin describing various embodiments of the invention, it is to bedefinitely understood that such were employed only to render thedescription more concrete and that they in no wise limit the scope ofthe invention except as required by the sub-joined claims.

I claim:

1. A starter-and-running circuit for fluorescent-lighting, comprising: asource of electrical energy having a predetermined frequency; at leastone conductor path in circuit therewith; a pair of lamp electrodesconnected in series in said conductor path; and a plurality ofreactormeans mutually interconnected in said conductor path andconnected with the electrodes, with the frequencyresponsecharacteristics of said means so correlated with reference to each otherand to the frequency of said source as to render their reactances equaland resonant with said source for instantaneous starting; at least oneof said reactor-means having impedance-characteristics so arranged andcorrelated with said source and with the remainder of the circuitry asto ballast the operat'on of the light after starting there being atuning condenser shunted across said plurality of reactor means anddisposed electrically anterior to said electrodes.

2. A circuit for fluorescent lighting, comprising: a source ofelectrical energy having a predetermined frequency; a conductor path incircuit therewith; a pair of lamp electrodes in said path and connectedin series with the source; a plurality of reactor-means mutuallyinterconnected in said conductor path with the frequency-responsecharacteristics of said means so correlated with reference to each otherand to the frequency of said source as to render their reactances equaland resonant with said source; a first one of said reactor-means beingan inductance electrically interposed in said conductor path in serieswith said electrodes and a second one of said reactor-means being acapacitor interposed in said 6 conductor path electrically anterior tosaid electrodes; there being a tuning capacitor shunted across saidconcluctor path in parallel with the first and second ones of saidreactor-means, and said tuning capacitor being dlsposed electricallyanterior to said electrodes.

3. A starter-and-runnng circuit for fluorescentlighting, comprising: asource of electrical. energy having a predetermined frequency; aconductor path in circuit therewith; at least one pair of lampelectrodes connected in series in said conductor path; and a pluralityof reactor-means mutually interconnected in said conductor path andconnected with the electrodes with the frequency-responsecharacteristics of said means so correlated with reference to each otherand to the frequency of said source as to render their reactances equaland resonant with said source for instantaneous starting; there being atuning condenser shunted across said plurality of reactor means anddisposed electrically anterior to said electrodes; one of said reactormeans being an inductance electrically interposed in said conductor pathin series with said electrodes and another of said reactor-means being acapacitor electrically interposed in said conductor path electricallyanterior to said electrodes.

4. A starter-and-running circuit for fiuorescentlighting, comprising: asource of electrical energy having a predetermined frequency; aconductor path in circuit therewith; at least one pair of lampelectrodes connected in series in said conductor path; and a pluralityof reactor-means mutually interconnected in said conductor path andconnected with the electrodes with the frequencyresponse characteristicsof said means so correlated with reference to each other and to thefrequency of said source as to render their reactances equal andresonant with said source for instantaneous starting; at least one ofsaid reactor-means having impedance-characteristics so arranged andcorrelated with said source and with the remainder of the circuitry asto ballast the operation of the light atfer starting; there being atuning condenser shunted across said plurality of reactor means anddisposed electrically anterior to said electrodes; one of said reactormeans being an inductance electrically interposed in said conductor pathin series with said electrodes and another of said reactor means being acapacitor electrically interposed in said conductor path electricallyanterior to said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS2,170,447 Edwards Aug. 22, 1939 2,231,999 Gustin et al. Feb. 18. 19412,586,402 Waguet Feb. 19, 1952 2,856,478 Kershaw Oct. 28, 1958 FOREIGNPATENTS 1,064,346 France May 12, 1954

